Source of the North Pacific “boing” sound attributed to minke whales
(Color online) Diagram of ship movement along the trackline, with visual and acoustic detection events. Axes are in decimal degrees of north latitude and west longitude. Ship position and direction, with the associated time, are shown at intervals along the trackline. Select bearing angles and lettered points indicate events described in the text. Numbered circles indicate acoustic position for sound source and/or visual location for minke whale. Gray lines represent acoustic bearing angle to sound sources, gray circles represent probable location of sound source based on continuous acoustic tracking. For clarity of presentation, we do not show all acoustic bearing angles.
Spectrogram of the (a) central boing and (b) eastern boing (sampling rate , FFT 8192, 75% overlap, Hanning window).
(Color online) Waveform of the central minke whale boing vocalization. The pulse repetition rate can be seen clearly in the expanded waveform (inset).
Frequency distribution for pulse repetition rates of 128 boing vocalizations measured for this study. Boing sounds with pulse repetition rates of are referred to as eastern boings, and those with pulse repetition rates of are referred to as central boings.
Map of the location of boing sources from the SWAPS, HICEAS, and STAR surveys. The central boings are represented by open triangles, the eastern boings are represented by open squares, and the ×’s indicate the location of calls too faint for measurement of the call characteristics. The dashed arrow indicates the approximate geographic division between the eastern and central boings.
Measurement of repetition rate and call duration for eastern and central boing vocalizations. One sample from each clear detection was measured and divided into Eastern and Central boing types. Measurements of 84 boing vocalizations associated with sighting number 267, B. acutorostrata are presented for comparison.
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